A method that has been successfully employed for insulating and/or protecting components susceptible to environmental damage, such as electrical components, is to overmold the component with either a thermoplastic or thermoset resin. In some cases, it is desirable to only partially overmold the component to protect a portion of the component while leaving another portion exposed. For example, in the case of plug and socket electrical component connectors that are mechanically and electrically connected to a printed circuit board, it is desirable to protect the circuit board in a housing, while leaving a portion of the electrical connector exposed for mating with a complementary connector. In such cases, it is desirable that the boundary or edge of the overmolding is well defined so that the overmolding does not cover any portion of the component that is designed to be exposed, yet completely covers those portions of the component that are intended to be overmolded.
Typically, overmolding involves shaping a flowable liquid or plastic resin under application of heat and pressure. In a known process shown in FIGS. 1 and 2, a plug type electrical component connector 10 is fabricated by first soldering or otherwise electrically and mechanically connecting a metal connector interface 12 to a printed circuit board 14, which may hold various electronic devices (e.g., flip chips, resistors, diodes, etc.) to form an assembly that is adhesively or otherwise secured to a backplate 16 (e.g., an aluminium backplate). The circuitry is protected by an overmolding 18 that together with backplate 16 form a housing. A portion of the connector interface 12 is covered by overmolding 18, while that portion of the connector interface that is mechanically coupled to a complementary connector is exposed.
It is desirable to have a sharply defined overmolding edge for providing an acceptable product appearance, and often for functional reasons as well. For example, in order to prevent mechanical interference during coupling of the connector 10 with its complementary connector, it is important that an edge 20 of overmolding 18 is precisely defined, i.e., that molding material (e.g., thermoplastic or thermosettable resin) does not flow past (or bleed-through) a shut-off 22 defined by abutting surfaces between an overmolding tool 24 and a component 12 that is to be partially overmolded.
In known processes, as depicted by FIGS. 1 and 2, it has often been necessary to carefully control the dimensions and tolerances of both the component 12 being partially overmolded and the overmolding tool 24 to provide nearly perfectly matched mating surfaces defining the shut-off 22, and/or to exert relatively high clamping forces on the overmolding tool 24 at the location of the abutting surfaces of the tool 24 and component 12. In some cases, this requires making the component stronger and more massive than might otherwise be required. Achieving a precisely defined overmolding edge may also place limits on the packing pressure (i.e., the internal pressure of the mold cavity defining surfaces of the overmolding tool), and/or the packing temperature (i.e., the temperature of the overmolding material in the mold cavity defined between the molding tool and the surface of the component that is being overmolded). This can place limitations on the types of overmolded materials that may be employed in a particular application.